The present invention relates generally to illumination devices and deals more specifically with a multi-color illumination device for use in backlighting a liquid crystal display (LCD) device.
It is well known in the art to provide backlighting for LCD devices which are either transmissive or transflective to provide a background against which the activated elements of the LCD are contrasted enabling a viewer to see the graphic, image or message displayed. The operation of LCD devices are well known to those skilled in the art and a more detailed description of their operation may be sought by reference to text books, literature and reference information available in the trade.
One well known drawback to LCD devices is the difficulty in viewing displayed images or messages and the like in very low light applications such as nightfall or dimly lit areas.
Since the human eye's sensitivity to red light is lower than its sensitivity to yellow/green light, displays having light in the red frequency spectrum allows the eye to adapt more readily in low light or nighttime applications. The human eye being more sensitive to yellow/green light makes light in the yellow/green frequency spectrum more suitable and visible in higher ambient light conditions.
It would be desirable therefore, to provide a multicolor illumination apparatus that may be used as backlighting for an LCD device to permit images, graphics, messages and the like to be more readily visible in differing light environments.
Conventional bi-color LED are generally well known and typically comprise LED dies bonded to respective ends of the leads of the device. A diffuser material forms a cap and encapsulates the leads and the dies to provide structural integrity and also to act as a light diffuser. Such conventional LED have a high profile and are generally unsuitable for backlighting applications.
It is a general aim of the present invention to provide a multi-color illumination apparatus that overcomes disadvantages of known multi-color lamps by providing a multi-color illumination apparatus that has a very low profile and on which uses diffusion tape to achieve uniform light distribution and avoid the light attenuation generally introduced by diffusion material used with conventional bi-color LEDs.
It is a further aim of the present invention to provide a multi-color illumination device which may be used as an alarm indicator, annunciator, attract mode device and in other applications in which a change of color is used as an indicating means to represent a given external condition.